Definitions, Sources and Explanatory Notes

 Category:   Petroleum Refining & Processing
 Topic:   Qualities of Crude Oil Input


Key Terms Definition
API Gravity An arbitrary scale expressing the gravity or density of liquid petroleum products. The measuring scale is calibrated in terms of degrees API; it is calculated as follows:
                Degrees API = (141.5 / (sp. gr. 60ºF / 60ºF)) - 131.5

The higher the API gravity, the lighter the compound. Light crudes generally exceed 38 degrees API and heavy crudes are commonly labeled as all crudes with an API gravity of 22 degrees or below. Intermediate crudes fall in the range of 22 degrees to 38 degrees API gravity.
Crude Oil A mixture of hydrocarbons that exists in liquid phase in natural underground reservoirs and remains liquid at atmospheric pressure after passing through surface separating facilities. Depending upon the characteristics of the crude stream, it may also include:
  • Small amounts of hydrocarbons that exist in gaseous phase in natural underground reservoirs but are liquid at atmospheric pressure after being recovered from oil well (casinghead) gas in lease separators and are subsequently commingled with the crude stream without being separately measured. Lease condensate recovered as a liquid from natural gas wells in lease or field separation facilities and later mixed into the crude stream is also included;
  • Small amounts of nonhydrocarbons produced with the oil, such as sulfur and various metals;
  • Drip gases, and liquid hydrocarbons produced from tar sands, oil sands, gilsonite, and oil shale.

  • Liquids produced at natural gas processing plants are excluded. Crude oil is refined to produce a wide array of petroleum products, including heating oils; gasoline, diesel and jet fuels; lubricants; asphalt; ethane, propane, and butane; and many other products used for their energy or chemical content.
    Crude Oil Qualities Refers to two properties of crude oil, the sulfur content and API gravity, which affect processing complexity and product characteristics.
    Petroleum Administration for Defense (PAD) Districts Geographic aggregations of the 50 States and the District of Columbia into five districts by the Petroleum Administration for Defense in 1950. These districts were originally defined during World War II for purposes of administering oil allocation. Description and maps of PAD Districts and Refining Districts.
    Refinery An installation that manufactures finished petroleum products from crude oil, unfinished oils, natural gas liquids, other hydrocarbons, and oxygenates.
    Refinery Input, Total The raw materials and intermediate materials processed at refineries to produce finished petroleum products. They include crude oil, products of natural gas processing plants, unfinished oils, other hydrocarbons and oxygenates, motor gasoline and aviation gasoline blending components and finished petroleum products.
    Sulfur A yellowish nonmetallic element, sometimes known as "brimstone." It is present at various levels of concentration in many fossil fuels.

    For definitions of related energy terms, refer to the EIA Energy Glossary.


  • Energy Information Administration, Form EIA-810, "Monthly Refinery Report".
  • EIA Forms & Instructions .
  • Background, Survey Methodology and Statistical Details .

  •   Explanatory Notes

  • Totals may not equal sum of components due to independent rounding.
  • Description and maps of PAD Districts and Refining Districts from the Petroleum Supply Monthly.